Not applicable.
This invention relates to the field of hand-held power saws and, more particularly, to a viewing window in a circular saw blade guard.
Hand-held power circular saws have been popular woodworking tools for many years. In a typical sawing operation, the user begins by marking or otherwise identifying a desired line along which to saw the material to be cut. The user then guides the saw during cutting, manually aligning the blade with the desired line of cut. Maintaining this alignment manually can be difficult because the typical circular saw has a blade guard that obscures the user""s view of the blade at the point of cutting and thus impedes the user""s ability to accurately align the blade with the desired cutting line.
To overcome this difficulty, one alternative has been to provide the circular saw with a guide slot. Typically located on the base of the saw, the guide slot is so aligned ahead of the blade in the forward cutting direction to provide a visual indication of the anticipated blade path through the workpiece. During operation, the user typically positions the saw so that the guide slot, and thus the blade, are aligned with the line of cut. This approach can provide a satisfactory cut, unless the saw blade is improperly aligned with the guide slot. A blade is typically oriented at a predesignated location on an arbor driven by the saw motor. Deviations from this orientation can occur causing misalignment between the blade and the guide slot. The guide slot will then incorrectly indicate the blade path, and the user relying on the guide slot will less likely cut the material as desired. Furthermore, since the blade is covered by the saw guard, the user cannot directly monitor the blade travel and, therefore, may not detect the misalignment until substantial cutting has occurred. As a result, the workpiece may be ruined.
To overcome these limitations, another alternative has been to supply the saw guard with a transparent viewing window covering an aperture in the saw guard. Such a window enables direct observation of the saw blade as it enters the workpiece, which in turn enables the user to better maintain a desired cutting path. For example, U.S. Pat. No. 1,830,579 to Wappat provides an observation opening in the side wall of a hand-held circular saw guard. However, the use of a side wall viewing port did not permit the user to saw from a comfortable position behind the saw and at the same time monitor the progress of the blade. Furthermore, to the extent the air currents directed towards the inside surface of the viewing pane were not sufficient to clear the pane of dust, manual clearing of the pane would be required which could more directly expose the saw blade.
A viewing window covering an aperture on the outside circumference of a circular saw blade guard is disclosed in U.S. Pat. No. 4,450,627 to Morimoto. This viewing window is coupled with the saw guard in a variety of ways, including by means of a press fit, a sliding fit or a side hinge. When the viewing window requires cleaning, however, it must either be removed or substantially opened, thereby exposing the saw blade area. After cleaning, if the user neglects to install or close the viewing window, sawing operation without the viewing window in place could occur. The user may not notice the missing viewing window until sawing operations have begun, and cut material could be ejected through the uncovered aperture. The side hinge structure disclosed in this patent allows complete exposure of the aperture in the saw guard.
To overcome these and other limitations in the prior art, an improved viewing window is desirable for a circular saw guard that is easily cleanable without requiring full exposure of the saw guard aperture.
Accordingly, it is an object of the present invention to provide a clear viewing window in a circular saw guard to cover an aperture in the guard so as to minimize exposure of the aperture during cleaning. A related object is to provide such a window that is easy to operate and inexpensive to manufacture and assemble.
It is a further object of the present invention to provide a clear viewing window for a circular saw guard so biased as to better ensure that the window returns to the closed position after cleaning.
It is a further object of this invention to provide a means for biasing a viewing window in a circular saw guard to the closed position on the outside of the saw guard and in a manner less likely to be affected by material generated during saw operation.
It is a further object of this invention to allow easy cleaning of a viewing window for a circular saw guard while greatly reducing any necessary exposure of the aperture. A related object is to provide a viewing window that is not easily removed from the saw guard and thus less likely to be misplaced.
According to the present invention, the foregoing and other objects are obtained by supplying a circular saw guard with a transparent viewing window whose movement is constrained so as to greatly reduce or eliminate exposure of the aperture during cleaning. In one embodiment, the viewing window is hingedly coupled with the guard to rotate outwardly from the periphery of the guard about an axis parallel to the rotational axis of the blade. In this embodiment, the window is supplied with a means for biasing it to a closed position during use. The window may also be carried in a frame and supplied with a means for limiting its travel to minimize exposure of the aperture during cleaning. In another embodiment of the invention, the viewing window may be larger than the aperture in the saw guard. Tabs forming slots may be provided in the saw guard proximal the aperture to receive a rectangular, planar window that can slide laterally between the use position and the cleaning position. Alternatively, the oversize window may be triangular in shape and pivot about a single point in the periphery of the saw guard. In another embodiment, the window may be approximately the same size as the aperture and be adapted to rotate along its longitudinal axis within the aperture between a use position and a cleaning position. In a further embodiment, the window may be fixedly mounted to the saw guard proximate a second aperture oriented to permit convenient cleaning of the inside surface of the window with a cleaning tool or compressed air introduced through the second aperture. During sawing operations, the second aperture may be covered with a removable plug retained in the second aperture by a press fit.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon an examination of the following, or may be learned by practice of the invention.